1. Field of the Invention
The present invention relates to a probe card for evaluating electrical characteristics of a semiconductor device or the like.
2. Description of the Related Art
In recent years, a plurality of chips are simultaneously tested in a wafer test with a probe card. There has conventionally been well-known a probe card shown in FIG. 4 having a contactor unit 300 including a contactor that establishes an electrical contact with a semiconductor device that is a subject to be tested and a substrate body 100, those of which are discretely fabricated. In this type of probe card, the substrate body 100 and the contactor unit 300 are electrically connected via an interposer 200.
A leaf spring 450 is fixed below the substrate body 100 so that its free end projects inwardly. The contactor unit 300 is supported by the leaf spring 450 from below and has parallelism adjusting means 500 for adjusting a parallelism of the contactor unit 300 provided so as to be in contact with the upper surface thereof.
The parallelism adjusting means 500 comprises a parallelism adjusting screw 520 threadedly secured to a reinforcing plate 650 fixed above the substrate body 100 so that its leading edge projects downwardly via a bore hole formed on the substrate body 100 and a ball 530 provided at the leading edge (downward) of the parallelism adjusting screw 520 so as to be in contact with the contactor unit 300, wherein the degree of parallelism of the contactor unit 300 is adjusted by changing the projection amount of the parallelism adjusting screw 520.
However, the contactor unit 300 may be deformed or broken in the conventional probe card, in the case where an adjusting stroke is excessively exerted on the parallelism adjusting screw 520 upon adjusting the degree of parallelism. Specifically, the leaf spring 450 that supports the contactor unit 300 has a great amount of pressure change in view of its characteristic, whereby excessive force is exerted on the contactor unit 300 to thereby produce a deformation or damage of the contactor unit 300 by this force. The deformation or damage of the contactor unit 300 has a problem of entailing non-uniform height of the contactor to thereby bring about a defective continuity to the subject to be tested. Similarly, the above-mentioned deformation or damage also has a problem of bringing about a defective continuity to the interposer 200.
Further, in the conventional probe card, the leaf spring 450 is arranged such that one end thereof is fixed to a leaf spring holder 460 fixed below the substrate body 100 and the inwardly projecting free end thereof supports the contactor unit 300. Additionally, reinforcing plates 640 and 650 are fixed independently at the inside and outside above the substrate body 100, the outward reinforcing plate 640 arranged at the position above the leaf spring holder 460 and the inward reinforcing plate 650 arranged at the position inwardly from the outward reinforcing plate 640 and above the free end of the leaf spring 450. Secured threadedly to this inward reinforcing plate 650 is the above-mentioned parallelism adjusting screw 500. Therefore, force exerted by the leaf spring 450 is exerted downwardly on the leaf spring holder 460, and exerted upwardly on the inward reinforcing plate 650. Because the outward reinforcing plate 640 positioned above the leaf spring holder 460 and the inward reinforcing plate 650 positioned above the free end of the leaf spring are independently provided as described above, the force by the leaf spring 450 is exerted on the substrate body 100 in different directions such as in an upward direction and a downward direction depending upon a place, whereby a deformation occurs on the substrate body 100 resulting from the force by the leaf spring 450. This deformation is likely to cause an electrically defective continuity.
Further, a temperature difference of each component member is produced in a test under a high temperature, whereby a warp of the overall substrate body is produced by the difference in a distortion amount of each component member based upon this temperature difference, thereby entailing a problem that electrical defective continuity is brought about as a result of this warp. This problem is eliminated by using a material having a coefficient of thermal expansion adjusted corresponding to the temperature difference of each component member so as to prevent the occurrence of the warp, but it is practically impossible to completely prevent the occurrence of the warp by finely adjusting the coefficient of thermal expansion of the material.